How to use When in laravel

So here is a peace of code without using when

if ($id != null)
{
    $result->where('users.id', $id);
}

$result->get();

If you want to do this using when you do it this way

$result->when($id,function( $q, $id){
    $q->where('users.id', $id);
});

$result->get();

Hope this helped